State troopers responded to the scene, on I-90 about 17 miles east of Ellensburg, at about 10:40 a.m. after receiving a report of a serious crash.
Arriving at the scene, they found a black 2003 Ford Escape lying on its side off the freeway.
One of the vehicle's five occupants, later identified as Austin M. Scott, 18, of Lake Forest Park, was found dead at the scene. The vehicle's four other occupants were injured.
All five crash victims were WSU students in a ride-share program heading home for the holidays.
An investigation found that the Escape had been heading west on I-90 at speeds too fast for the icy conditions. The driver, a 19-year-old Kent woman, lost control of the vehicle and it veered off the roadway to the left, rolling over and landing on its side.
The driver and three passengers - an 18-year-old Kent woman, a 20-year-old Poulsbo woman and an 18-year-old Omak man - were taken to Kittitas Valley Hospital. The 18-year-old Omak was later taken to Harborview Medical Center for treatment of more serious injuries.
Alcohol and drugs were not a factor in the accident.
The crash remains under investigation.